Nippon Steel and U.S. Steel said Wednesday they have finalized their “historic partnership,” a year-and-a-half after the Japanese company first proposed its deal to buy the iconic American steelmaker for nearly $15 billion.

The pursuit by Nippon Steel for the Pittsburgh company was buffeted by national security concerns and presidential politics in a premier battleground state, delaying the transaction for more than a year after U.S. Steel shareholders approved it. It also forced Nippon Steel to expand the deal, including adding a so-called “golden share” provision that gives the federal government a say in some matters.

The combined company will become the world's fourth-largest steelmaker, and bring what analysts say is Nippon Steel's top-notch technology to U.S. Steel's antiquated steelmaking processes. In exchange, Nippon Steel gets access to a robust U.S. steel market, strengthened in recent years by tariffs under Donald Trump and Joe Biden, analysts say.